Tectono-Stratigraphic Sequence and Basin Evolution in Southern Songliao Basin

The southern Songliao Basin tretch across several geotectonic units such as Xingmeng-Jihei orogen, North China Plate,and increased convergent plate boundary in north border of North China Plate,and it mainly develop small scale sedimentary basins in late-Mesozoic who have the character of multistage evolution and intense reconstruction of later stage,and people have found oil and gas fields in Zhanwu, Changtu and Manghan sag.Analysing its tectono-stratigraphic sequence and basin evolution history is an important foundation of acquainting region of interest's oil and gas resources and expanding oil and gas discovery.Based on the region of interest's newly seismic profiles,drilling and peripheral 1∶250000 regional geological mapping,the paper builds up the district stratigraphic system.According to the development characteristics of regional unconformity interface,subdivide tectono-stratigraphic sequence and basin evolution stage,then discuss basin formation history.Studies suggest that the sedimentary basin of southern Songliao Basin is formed under control of the development of circum-Pacific tectonic system;It develop three regional unconformity interfaces,including the bottom of Lower Crataceous Yixian Formation,the bottom of Lower Crataceous Quantou Formation and the bottom of Upper Crataceous Sifangtai Formation,according to them,subdivide four sets of tectono-stratigraphic sequence as well as basement structural layer,rift structural layer,depression structural layer,structural layer of basin inversion;And accordingly,the southern Songliao Basin undergo four basin evolution stages,which are basement formation period,Early Crataceous rift period,late-Early Cretaceous-Late Cretaceous depression period,Late Cretaceous Basin inversion period.The tectonic evolution of southern Songliao Basin controlled development of its petroleum system and distribution regularity of oil and gas.Reservoir evolution experienced both deeply buried into hydrocarbon accumulation and adjustment process of later uplift, furthermore,reservoirs have characteristics ofsmall scale,encircling distributed by oil source sub-sag. Rift structural layer who has large oil and gas resource potential is main purpose of the present exploration layer of southern Songliao Basin,whose petroleum geological condition is superior,and has good prospects of oil and gas exploration.